In the field of clinical surgery minimally invasive surgical operations are growing in importance. Only a few years ago relatively large areas of the operative site were opened up even for minor surgical operations in order to enable the surgeon to navigate by means of natural landmarks. It may be observed that today a large number of these surgical operations are performed by means of laparoscopy and optical support in the form of endoscopy. In some areas of medicine, e.g. urology, gynecology or cardiology, robot-supported surgery as a development of traditional laparoscopy has been on the increase in the meantime and is in the process of establishing itself.
In the case of laparoscopy in the traditional sense, instruments which are used to carry out a medical measure inside a patient are introduced into the patient at least partially by means of a trocar and operated or controlled manually by a surgeon.
In the case of robot-supported surgery, a corresponding instrument is located on a manipulator arm of an endoscopic robot. Here too the instrument passes from outside the patient into the inside of the same. The robot arm always remains outside the patient. The robot or its control system therefore assumes the actual control of the instrument. The surgeon in turn controls only the robot with the aid of an operating interface. A known endoscopic robot is e.g. the “Da Vinci” system made by the company “Intuitive Surgical”.
The known system constitutes a so-called tele-operated robot assistance system, in which a surgeon manually performs movement inputs on an operator console. The robot then transmits the scaled movements via appropriate kinematics to the instruments inside the body of the patient. Such systems play a decisive role in market development. There are numerous possible solutions to the design of the kinematics of the assistance system which have hitherto been characterized by an inconveniently large requirement for space.
Namely it is known, e.g. from the aforementioned “Da Vinci” system, not to provide the required mobility in the instrument itself but by means of the part of the endoscopic robot located outside the patient, namely the manipulator arm. The manipulator arm therefore constitutes the prime extracorporeal positioning unit for the instrument. The instrument itself is more or less rigid and also fixed rigidly to the manipulator arm. As a rule, the entry point through the trocar forms a pivotal point for the available movements. In any case, the actual treatment head of the instrument can be moved on the instrument, e.g. in the form of a pair of scissors or a gripper which can be operated. The instrument itself therefore only displays a single degree of freedom, e.g. opening or closing of the arms of the gripper.
The known “Da Vinci” system has up to four manipulator arms which can be moved individually. In order to realize the aforementioned degrees of freedom of the instrument movement, these are elaborately constructed and require a large volume of space in which to move.
In contrast, it is also possible to counteract this disadvantage using newer designs. For example, it is possible to propose improved instruments which themselves enable greater freedom of movement than the rigid instruments known hitherto.
The manipulator arms can then provide less scope for movement and as a result can be designed more simply and with a smaller requirement for space.
Intrinsically mobile instruments also make it possible to economize on manipulator arms as several instruments can be held on one arm which nevertheless can then be moved relative to each other on account of their intrinsic mobility. As a result of the fact that the instruments or endoscopes themselves have greater degrees of freedom of movement, the working area required by the endoscopic robot or its manipulator arm outside the body therefore remains limited. The principal part of the surgery movement is replaced by a greater degree of kinematic freedom within the operative site.
Depending on the distribution of the degrees of freedom across the manipulator arm and instrument, the combination of a mobile instrument with a corresponding manipulator arm results in an endoscopic robot with at least partial intracorporeal operation.
The challenge of the latter approaches now consists of realizing the multiplicity of instruments and degrees of freedom of movement in the case of a small instrument diameter. Namely, the instruments must as a rule be introduced into the patient by means of a trocar with an internal diameter of approx. 10 mm maximum or be moved through the trocar.
Another problem is that a business model can increasingly be found in relation to medical instruments in which the instruments are supplied as one-time-use instruments, so-called disposables. This results in a demand for instruments with a low cost position that can at the same time be sterilized with ease. All of the aforementioned challenges have hitherto met with realization problems.
In a mobile instrument it is conceivable to drive the axes of the instrument degrees of freedom principally by means of wire cable designs, wherein the wire cables are finally driven by the endoscopic robot. The aim of this approach is to remain as cost-effective as possible on the basis of a desired disposable design. For every degree of freedom in the instrument at least two wire cables must be fed through the instrument structure in order to be able to realize both directions of movement at a force or torque which can be dosed.
For an instrument with a scope of movement which is intended to cover five degrees of freedom and a mobile treatment head with one function, ten plus two wire cables must therefore be provided at the most unfavorable position, namely between the robot arm and the first joint. Both the latter then serve to provide end effector functionality, e.g. the actuation of a pair of scissors or a gripper. All the wire cables must be fed through the structure at least at the fastening end of the instrument. This is expensive.
Additional axes of motion can be brought about by moving the mounting bracket of the instrument on the robot arm itself. However, these do not constitute any real mobility of the instrument, in other words relative to the robot arm.
To be sure, such an instrument can be constructed, for example, with a diameter of 8 mm. However, no installation space of any kind is left, for example, to incorporate another electrical power cable into the instrument as would, for example, need to be supplied at the tip of the instrument for an HF blade as a treatment head.
On the other hand, the sterilizing capability of such a design, for example precisely in the area of a bend or a joint, must be called into question. Scalability to yet more degrees of freedom with the same or an even smaller diameter is in all probability not currently practicable in terms of technology.
Alternatively, the use of direct drives with sufficient power density or upstream gears for each individual joint is conceivable in corresponding instruments. However, a disposable design for such an instrument does not at least appear to be feasible on account of the anticipated costs. In addition, available direct drives, for example piezoelectric drives with appropriate performance data, have a space requirement which already takes up the majority of the diameter of an instrument. Additional energy and signaling lines which are to be fed past the direct drive are therefore difficult to accommodate in the interior of the instrument. The advantage of this approach, however, resides in the fact that with a constant diameter such a system design is scalable and both the structural and production complexity of the instrument is reduced.